Ground strain gauge

ABSTRACT

A ground strain gauge is provided in which there is a working liquid storage tank which, in conjunction with shutoff valves at the inlet and outlet sides of two measuring cylinders, makes it possible to increase the working liquid volume in a flexible chamber inserted in a hole in the ground to be tested.

United States Patent Ruppeneit et al. Nov. 20, 1973 [5 GROUND STRAINGAUGE 3,533,283 10/1970 DaRocha et a1. 73/88 E [76] Inventors:Konstantin Vladimirovich g j zzi' i Ruppeneit, f y y? 3, 65; 3,481,1882/1969 Mon' 73 84 Evgeny semenovlch g 3,442,123 5/1969 Broise 73/151Glagoleva 24, korpus 2, kv. 14, both if 4 3 z f i g FOREIGN PATENTS ORAPPLICATIONS enIsov, ar ovaya v. Ljubertsy Moskovskaya oblasti; 501,18611/1954 Italy 73/84 Alexandr Vasilievich Golubev, Dokukma M of PrimaryExaminerC harles A. Ruehl Attorney-Waters, Roditi, Schwartz & Nissen[22] Filed: May 20, 1971 21 Appl. N0.: 145,304

[57] ABSTRACT [52] US. Cl 73/88 E A ground Strain gauge is provided inwhiah there is a [51] Int. Cl. GOln 3/10 working liquid storage tankwhich in conjunction with [5 8] Field of Search 73/88 E, 84, 94, shutoffvalves at the inlet and outlet Sides of two 73/89 149 suring cylinders,makes it possible to increase the working liquid volume in a flexiblechamber inserted [56] Reierences cum in a hole in the ground to betested.

UNITED STATES PATENTS 2,957,341 10/1960 Menard 73/84 4 Claims, 1 DrawingFigure PATENTED NOV 20 I973 SOL H. Z

GROUND STRAIN GAUGE This invention relates to measuring means and, moreparticularly, to ground strain gauges.

Ground strain gauges (soil strainmeters) are known in the art, whichcomprise a chamber with flexible side walls, wherein an appropriateliquid, such as water, oil, and the like, is forced into said chamberfrom a measuring cylinder by pressurized air, and said chambercommunicates with a pressurized air source via said measuring cylinder.

These prior art gauges operate on the principle of measuring the volumeof a liquid pumped into the instrument chamber disposed in a bore holein the ground to be tested.

However, the known soil strain gauges suffer from the draw-back of beinginadequately versatile, inasmuch as a given gauge does not lend itselftoemployment for testing various types of grounds that exhibit widelyvarying deformation characteristics.

It is an object of the present invention to avoid this disadvantage ofthe known gauges.

The present invention aims at providing the possibility of increasingthe working volume of the liquid in the course of a single test by usingthe measuring cylinder repeatedly.

With this aim in view, the invention resides in the provision of agorund strain gauge comprising a chamber with flexible side walls intowhich a liquid is fed by a pressurized gas from a measuring cylinderwherein, according to the invention, above the measuring cylinderprovision is made for a built-in, closed liquid stor:- age tankcommunicating with a pressurized gas source, the top and the bottom ofsaid tank being connected by pipelines to the top part of the measuringcylinder, and the inlet and the outlet side of said measuring cylinderbeing furnished with shutoff valves.

To render the process of pumping the liquid to the flexible chamberuninterrupted, the present gauge should preferably incorporate at leastone additional measuring cylinder placed in parallel with the firstmeasuring cylinder and also having shutoff valves at its inlet andoutlet sides.

In case the gauge, according to the invention, is employed for measuringthe deformation of dense grounds, it is expedient to enhance thesensitivity of the instrument, without resorting to major readjustmentsthereof, by using measuring cylinders of dissimilar diameters.

In the following, the present invention is illustrated by a detaileddescription of a specific embodiment thereof with reference to theaccompanying Drawing, in which the sole figure is a sectional view ofthe ground strain gauge, according to the invention.

The present gauge comprises a chamber 1 with flexible side walls 2.There are two measuring cylinders 3 and 4 of dissimilar diameters, saidmeasuring cylinders being placed in parallel with each other and beingconnected to the chamber 1 by a pipeline 5. A working liquid (water)storage tank 6 is built into the gauge above the level of the measuringcylinders 3 and 4, said tank 6 communicating with a pressurized gassource by a pipeline 7. The bottom of the tank 6 is connected to themeasuring cylinders 3 and 4, while the top of the tank 6 communicatesvia a pipeline 9 with the measuring cylinder 3. The cylinder 3 is, inturn, connected to the second measuring cylinder 4 by means of apipeline 10. At the inlet and outlet sides of the measuring cylinders 3and 4, provision is made for shutoff valves ll, 12 and 13, 14respectively.

Prior to commencing tests, the working liquid (water) is charged intothe gauge so as to fill completely the chamber 1 and most of the volumeof the measuring cylinders 3 and 4 and of the storage tank 6.

When the ground strain gauge is used to test soft soils, with theshutoff valves 11, 13 and 14 closed, pressurized gas (nitrogen) isadmitted via the pipeline 7 in order to displace the working liquid fromthe measuring cylinder 3 into the chamber 1. Water inflow to the chamber1 causes the flexible walls to expand and overcome the resistanceoffered by the ground being tested. Ground deformation is determinedfrom the variation of the water volume in the measuring cylinder 3 at agiven gas pressure.

When the present gauge is employed for testing more dense soils, it ispreferable to resort to the measuring cylinder 4, which has a smallerdiameter, and is, therefore, more suitable for recording accuratelywater volume variations.

In the present gauge, provision may be made for three, four or moremeasuring cylinders, depending upon the requisite accuracy range ofground strain measurements.

In case the ground under test is extremely soft and the water volume inthe cylinder 3 is inadequate at a given gas pressure, the valve 12should be close and the valve 11 opened in order to replenish the waterin the cylinder 3 from the storage tank 6.

To avoid test discontinuation while the water is being added-to thecylinder 3, the valve 14 should be opened to allow water from thecylinder 4 to be displaced into the chamber 1.

If necessary, the operation of alternative replenishment of thecylinders 3 and 4 with water may be carried out repeatedly.

After the readings have been taken, the valves 1 l, 12, 13 and should beclosed and the system depressurized, the excess pressure in the chamber1 forcing the water therefrom into the measuring cylinders 3 and 4 andthe storage tank 6.

We claim:

1. A ground strain gauge which comprises a chamber with at least oneflexible side wall; a measuring cylinder having an inlet at one endthereof and an outlet at its other end; means for connecting saidcylinder outlet to said chamber; a closed storage tank disposed abovethe level of said measuring cylinder; means for communicating the top ofsaid tank with the top of said measuring cylinder; means for connectingthe bottom of said tank to said cylinder inlet;.shutoff valves mountedat the inlet and the outlet of said measuring cylinder; and apressurized gas source connected to the top of said storage tank.

2. A ground strain gauge according to claim 1, wherein there is at leastone additional measuring cylinder having an inlet and outlet withshutoff valves and disposed parallel to the first said measuringcylinder, each additional cylinder being connected by its valved inletto the bottom of said tank and by its valved outlet to said chamber.

3. A ground strain gauge according to claim 2 wherein said measuringcylinders have dissimilardiameters.

4. A ground strain gauge according to claim 2, wherein means areprovided for communicating the tops of the cylinders.

1. A ground strain gauge which comprises a chamber with at least oneflexible side wall; a measuring cylinder having an inlet at one endthereof and an outlet at its other end; means for connecting saidcylinder outlet to said chamber; a closed storage tank disposed abovethe level of said measuring cylinder; means for communicating the top ofsaid tank with the top of said measuring cylinder; means for connectingthe bottom of said tank to said cylinder inlet; shutoff valves mountedat the inlet and the outlet of said measuring cylinder; and apressurized gas source connected to the top of said storage tank.
 2. Aground strain gauge according to claim 1, wherein there is at least oneadditional measuring cylinder having an inlet and outlet with shutoffvalves and disposed parallel to the first said measuring cylinder, eachadditional cylinder being connected by its valved inlet to the bottom ofsaid tank and by its valved outlet to said chamber.
 3. A ground straingauge according to claim 2 wherein said measuring cylinders havedissimilar diameters.
 4. A ground strain gauge according to claim 2,wherein means are provided for communicating the tops of the cylinders.